Microwave-ultra-fast recovery of valuable metals from spent lithium-ion batteries by deep eutectic solvents.

[Display omitted] • LiCoO 2 powder leaching was achieved by microwave via deep eutectic solvent. • Two kinds of deep eutectic solvents were used in this microwave-ultra-fast leaching. • Over 90 % of Li and Co were leached at 4 min and 160 W by adding urea / lactic acid. • Li and Co leaching were controlled by shrinking core model of chemical reaction. The large-scale use of electric vehicles produced massive discarded lithium-ion batteries, containing many recyclable valuable metals and toxic and harmful substances. Biodegradable and recyclable deep eutectic solvent (DES) is considered a green recycling technology for spent LIBs. Herein, we proposed a microwave-enhanced approach to shorten the leaching time in the urea/lactic acid: choline chloride: ethylene glycol DES system. The dipole moments induced by urea or lactic acid on LiCoO 2 surface increased over two orders of magnitude under the high electric field. Because of this, over 90 % of Li and Co can be fast leached at 4 min and 160 W in the urea/lactic acid: choline chloride: ethylene glycol DES system. Meanwhile, we established two models to explain the leaching mechanism of metal ions from their leaching kinetics and micro-level behavior, and named them dot-etching and layer-peeling processes, respectively. By further analyzing, we found that the dot-etching can be attributed to the synergistic effect of reduction and coordination, which caused the surface of leaching residues porous. The layer-peeling process depends on neutralization, and the leaching residues had a smooth surface in this process. This work highlights the effect of microwave-enhanced strategy and DES surface chemistry on spent electrode materials recovery. [ABSTRACT FROM AUTHOR]